1. Field of the Invention
The present invention relates to a sheet guiding apparatus configured to guide to a predetermined position a sheet adsorbed to a supporting surface.
2. Description of the Related Art
There is conventionally known a sheet sorting apparatus configured to guide a sheet fed along a feeding path to another path branched from the feeding path. Such an apparatus is, for example, disposed on a sheet-discharged portion of a sheet-discharge device of a printer and is used as a sorter which sorts a plurality sets of recorded sheets onto a plurality of sheet-discharge trays. Such a sorter is disclosed in Patent Document 1 (U.S. Pat. No. 6,295,081 B1 and U.S. Pat. No. 6,443,449 B1 corresponding to JP-A-11-228013), Patent Document 2 (JP-A-08-324876), and Patent Document 3 (U.S. Pat. No. 6,478,298 B1 corresponding to JP-A-2002-137866).
Each of the apparatuses disclosed in Patent Documents 1 and 2 includes a flap provided in a feeding path and a solenoid for driving the flap. In each apparatus, when the flap is operated by the solenoid, a sheet is moved or enters into one of paths guided by the flap. Further, an apparatus disclosed in Patent Document 3 is provided with a gate for guiding a sheet to a desired one of paths only when the sheet is reversely fed. In this apparatus, a direction in which the sheet passed through the gate is fed is inverted, whereby the sheet is guided to the desired path.
However, in each apparatus disclosed in Patent Documents 1 and 2, the solenoid for operating the flap is needed in order to sort the sheet, resulting in that the apparatus cannot achieve downsizing and weight reduction. Further, in the apparatus disclosed in Patent Document 3, a next sheet cannot be moved into during the reverse feeding of the sheet though the solenoid is not needed. Thus, a distance between a preceding sheet and the next sheet unfortunately becomes relatively large, and thus a sheet feeding processing cannot become faster.
Each of Patent Document 4 (US 2006/0279621 A1 corresponding to JP-A-2005-15227), Patent Document 5 (JP-A-53-114424), and Patent Document 6 (U.S. Pat. No. 7,259,955 B2 corresponding to JP-A-2004-120921) discloses sheet feeding apparatus using static electricity. In this apparatus, the static electricity is generated between a sheet and a supporting member formed by a component such as a sheet feeding belt and a sheet supplying rotatable member, and the sheet is fed while being adsorbed to the supporting member by the attractive force (a coulomb force) due to the static electricity. The apparatus disclosed in Patent Document 4 is configured such that a direction in which the sheet adsorbed to the sheet feeding belt is fed is changed by a driven roller provided on a downstream side in a sheet feeding direction. Specifically, when the sheet passes through an upper surface of the driven roller, the sheet is disengaged from the sheet feeding belt by a curvature of the driven roller (actually, a curved portion of the sheet feeding belt) and stiffness of the sheet itself. The disengaged sheet is transferred to a sheet-discharge tray located on a downstream side and is moved to the sheet-discharge tray (with reference to paragraph [0050] in Patent Document 4).
However, in a mechanism in which the sheet is disengaged from the sheet feeding belt like the apparatus disclosed in Patent Document 4, the sheet can be disengaged only at a curved portion of the sheet feeding belt. In other words, the sheet cannot be disengaged at straight portion of the sheet feeding belt. Thus, where the feeding path is branched from the straight portion of the sheet feeding belt, the sheet cannot be guided to the branched path. Further, under a circumstance where a condition in which the sheet is disengaged from the sheet feeding belt is different between a case where a thin sheet having low stiffness is fed and a case where a thick sheet having high stiffness is fed, where the curvature of the driven roller has to be made larger to suit the thin sheet, a design freedom of the driven roller, the sheet feeding belt, and so on is limited. On the other hand, where the curvature of the driven roller is made smaller to suit the thick sheet, there is caused a problem in which the sheet is not disengaged from the sheet feeding belt when the thin sheet is fed. This problem may occur not only for an apparatus having a mechanism in which a sheet is supported by a sheet feeding belt but also for a general apparatus having a mechanism in which a sheet is guided to another position from a supporting surface by which the sheet is supported by an attractive force due to static electricity.